Editing Identification key (section)

== Types of keys ==
Identification keys are sometimes also referred to as ''artificial keys'' to differential them from other diagrams that visualize a classification schemes, often in the form of a key or tree structure. These diagrams are called ''natural keys'' or ''synopses'' and are not used for identifying specimens. In contrast, an artificial identification key is a tool that utilizes characters that are the easiest to observe and most practical for arriving at an identity.<ref name=":3" />{{Rp|page=7}}<ref name=":5" />{{Rp|page=225}} Identification keys can be divided into two main types.

=== Single-access key ===
{{Main|Single-access key}}
[[File:Screenshot from 2024-10-20 20-19-32.png|thumb|300x300px|User interaction steps in a single-access key. The sequence of steps follow the data structure.]]
A single-access key (also called a sequential key or an analytical key), has a fixed structure and sequence. The user must begin at the first step of the key and proceed until the end. A single-access key has steps that consist of two mutually exclusive statements (''leads'') is called a ''dichotomous key''. Most single-access keys are dichotomous.<ref name=":0" /> A single-access key with more than two leads per step is referred to as ''polytomous.''<ref name=":4">{{Cite book |last1=Hagedorn |first1=Gregor |url=https://www.openstarts.units.it/server/api/core/bitstreams/e5c6bdd8-c0ec-4442-bda8-61f66dd43b05/content |title=Tools for Identifying Biodiversity: Progress and Problems |last2=Rambold |first2=Gerhard |last3=Martellos |first3=Stefano |date=2010 |publisher=Edizioni Università di Trieste |isbn=978-88-8303-295-0 |editor-last=Nimis |editor-first=P. L. |pages=59–64 |chapter=Types of identification keys |editor-last2=Vignes Lebbe |editor-first2=R |chapter-url=https://www.openstarts.units.it/server/api/core/bitstreams/d6c3dc5f-17a1-478b-beab-31464b220ce1/content |chapter-format=PDF |via=openstarts.units.it}}</ref>

==== Presentational variants ====
Dichotomous keys can be presented in two main styles: linked and nested. In the linked style (also referred to as ''open,'' ''parallel, linked, and juxtaposition''<ref name=":4" />{{Rp|page=63}}), each pair of leads (called a ''couplet'') are printed together. In the nested style (also referred to as ''closed,'' ''yoked, and indented<ref name=":4" />{{Rp|page=63}}''), the subsequent steps after choosing a lead are printed directly underneath it, in succession. To follow the second lead of the couplet, the user must skip over the nested material that follows logically from the first lead of the couplet.<ref name=":3">{{Cite book |last=Pankhurst |first=R. J. |title=Biological identification: the principles and practice of identification methods in biology |date=1978 |publisher=University Park Press |isbn=978-0-8391-1344-7 |location=Baltimore |pages=11–28 |chapter=Conventional Identification Methods}}</ref> Nested keys are more commonly known as ''indented'', but unfortunately this refers to an accidental (albeit frequent) rather than essential quality. Nested keys may be printed without indentation to preserve space (relying solely on corresponding lead symbols) and linked keys may be indented to enhance the visibility of the couplet structure.<ref name=":4" />{{Rp|page=63}}

=== Multi-access keys ===
{{Main|Multi-access key}}
[[File:Multi-access_key.png|alt=Diagram of possible progressions through a multi-access key.|thumb|300x300px|User interaction steps in a multi-access key. The sequence of steps is determined by the user.]]
A multi-access key (free-access key,<ref name=":4" /> or polyclave<ref name=":1" />) allows a user to specify characters in any order. Therefore, a multi-access key can be thought of as "the set of all possible single-access keys that arise by permutating the order of characters."<ref name=":4" />{{Rp|page=60}} While there are print versions of multi-access keys, they were historically created using punched card systems.<ref name=":1" /> Today, multi-access keys are computer-aided tools.<ref name=":4" />{{Rp|page=61}}